1. Field of the Invention
The present invention relates to a chain tensioner having a tensioner body with a plunger bore, a plunger slidably fitted in the plunger bore, an arm provided to the tensioner body, and a guide shoe pressed by the plunger and pivotally supported on the arm.
2. Description of the Related Art
Chain tensioners have hitherto been commonly used for maintaining correct tension in a chain, for example, in a chain guide system that slidably guides a transmission chain such as an endless roller chain passing over respective sprockets of a crankshaft and a cam shaft, or a crankshaft and a drive shaft of an auxiliary machine, inside an engine room, by means of a guide shoe. The chain tensioner is used to tighten a pivoting chain guide having the guide shoe to maintain correct tension.
In such a chain guide system, sometimes it is necessary to install a mechanism for maintaining correct tension in the chain between close-spaced shafts (such as a crankshaft and a drive shaft of an auxiliary machine that are often designed to be close to each other) or in a confined peripheral space.
For such application, there is known a compact integrated chain tensioner with an arm formed on the tensioner body and a guide shoe pivotally supported directly on the arm.
Generally, the common structure for pivotally supporting a guide shoe directly on the arm is a through hole formed both in the guide shoe and arm and a pin passed through these through holes. This structure, however, requires a large number of components, and a large number of process steps during assembly such as alignment of the through holes, insertion of the pin, and retention of the pin, etc.
An alternative structure has been proposed to reduce the number of components and to simplify the assembling process (see, for example, Japanese Patent Application Laid-open Nos. 2010-107021 and 2006-132761), wherein one of the arm and the guide shoe has a pivot pin part to mate with a bushing part formed on the other, so that no separate pin member is required.